This invention generally relates to the method and apparatus for determining the type of battery supplying power to battery operated equipment and being charged by battery chargers. This invention more particularly relates to a method and apparatus which will detect the type of battery connected to a circuit of the battery operated equipment on the basis of a predetermined voltage potential supplied at a test terminal of the battery and which will select one or more operating parameters for the using or charging equipment to optimize battery performance.
Operationally, batteries of different types (such as those characterized by chemical components--Lithium, NiCd, Lead Acid, Alkaline, etc.--and those characterized as rechargeable or non-rechargeable) exhibit different end of life voltage characteristics and effective series resistances. Since different types of batteries can be interchangeably used to provide power for the same equipment (i.e. for a Cellular Portable Telephone), knowledge of the type of battery may be useful to the equipment in establishing operating parameters such as transmitter output power or in warning the user of a "low battery" condition.
Nonrechargeable battery types should not be subjected to recharging attempts. Battery types that can be charged should be charged at differing rates and with differing conditions. A battery charger which accepts all battery types ideally should adapt the rate of charge (charge current) and the types of charge controls used in accordance with the battery type. Although it is known that the charge rate of a battery may be optimized in accordance with the charge capacity of the battery (U.S. Pat. No. 4,006,396 discloses a battery and charger apparatus which employs an electrical element within the battery housing itself to provide a signed characteristic of the battery's charge state and which is employed by a charger circuit to control the rate of charge for the battery). This optimization is not changeable based on battery type and is limited to rate-of-charge determination. Therefore, it would be useful for a battery charger to automatically recognize the battery type which is to be charged and adapt its charging parameters accordingly.